In a variety of business scenarios, it can be important to collect heterogeneous groups of items. As one example, it can be important to items specified in a remotely-placed order for delivery. As an alternative to purchasing merchandise in person at a physical store, shoppers may also place orders remotely for merchandise to be delivered. Such remote orders may be placed by a variety of means, such as by making a telephone call to a merchant, or interacting with a merchant's web site.
An order generally identifies one or more ordered items, and specifies delivery information for use in addressing and shipping one or more packages containing the items identified in the order. For some orders, all of the items in the order are shipped in a single shipment. In some cases, however, the items in a single order are divided into two or more separate shipments, such as for orders containing items not all available for shipment from the same distribution center at the same time.
Each shipment is typically delivered from a single distribution center. In a distribution center, items are “picked” to use in fulfilling shipments to be delivered from that distribution center—that is, they are manually removed from storage locations where they reside, such as particular bins or shelves. After being picked, items are conveyed to an assembly point where the items needed for each shipment are collected. In some cases, a sorting machine collects the items needed for each shipment. A typical sorting machine has a number of bins that are each used to collect the items for a single shipment. Accordingly, at any given time, the sorting machine may be collecting items for up to a number of shipments equal to the number of bins. After the sorting machine collects the items needed for a given shipment, the sorting machine discharges the items for packing of the shipment, such as into one or more boxes.
Conventionally, shipments are picked in batches whose size was equal to the number of sorting machine bins. At the starting time for a batch, all pickers are sent out with a list of items to pick during that batch. Each picker picks the items on his or her list, then waits for the current batch to conclude and the next batch to start, at which time all pickers receive a new list of items to pick.
Using this approach, the sorting machine often operates with significant numbers of unused bins, and thus with significant unused capacity. Furthermore, pickers are sometimes blocked, waiting on the next batch to begin. This underutilization of the sorting machine is particularly acute near the beginning of batches, before significant numbers of items have begun to arrive at the sorting machine; near the end of batches, after a significant fraction of the shipments in the batch have been discharged; and between batches, when all of the shipments in the preceding batch have been discharged, and no items have been picked for shipments in the upcoming batch. As the processing capacity of many distribution centers—measured by number of shipments processed in a given time period—is materially constrained by the utilization rates of their sorting machines, such underutilization often prevents these distribution centers from reaching higher levels of productivity, despite a willingness to devote additional picking resources to their operation.
In view of this significant disadvantage of conventional approaches to picking items for inclusion in shipments, a new approach to picking items that more fully and evenly utilizes the capacity of sorting machines would have significant utility.